This present invention relates to the use of absorbent sponge-like materials made from essentially fat-free foamable natural products such as animal proteins and plant polysaccharides, which products are biodegradable and capable of attracting and retaining oils, especially hydrocarbon oils and hydrocarbon fuels, and to the removal of such oils and fuels from aqueous media, or aqueous-wetted surfaces. The need for such methods, in association with cleanup efforts for the marine environment, is readily apparent in view of the high incidence of offshore oil spills and the ineffectiveness of many known cleanup methods. Similarly, significant offshore water pollution may be caused by shipping vessels and oil tankers as they routinely clean out the dregs of their holding tanks and bilges into the open water. Furthermore, under or aboveground storage tank facilities, and other land-based sites which store and maintain fuel and other hydrocarbon oils, often leak or spill their contents resulting in ground water and/or water table contamination.
This invention also relates to the absorption of oils, including hydrocarbon oils and fuels in areas wholly unrelated to petroleum spill cleanup and recovery. The present invention is equally effective for any operation requiring the separation or absorption of any hydrocarbon oil or fuel from any aqueous media or aqueous-wetted surface such as the sand or rocks that occur at a shoreline.
The need for a complete, workable solution to the recurrent problem of oil spill and other hydrocarbon oil contamination to inland waterways, oceans and shorelines has led to the discovery of numerous devices and processes aimed at oil spill recovery and containment. Unfortunately, most of the devices or processes known in the art fail to achieve this goal. While some oil containment operations may immobilize and sink floating offshore contaminants, such a remedy does not adequately address the subsequent harm caused to the surrounding environment as well as the ocean floor. Similarly, while many known processes and devices facilitate the immobilization and incineration of floating non-polar contaminants, the concomitant air pollution is seldom an acceptable side effect.
Recently, oil "digesting" bacterial, yeast and fungal microorganisms have been applied to assist in oil spill biodegradation. The use of these organisms for petroleum biodegradation is disclosed, inter alia, in U.S. Pat. Nos. 3,769,164; 3,870,599; 3,843,517 and 3,871,956. However, these organisms work slowly, if at all, in most marine environments. Such organisms often require substantial oxygen to metabolize oils and it is often impossible to satisfactorily oxygenate an entire surface spill. In addition, many of these organisms work best, if at all, on placid bodies of water. Often, small wave action is enough to impair any significant amount of "digestion". Therefore, the use of such microorganisms is often impractical for the treatment of spills.
The present invention further represents a significant unexpected advancement in the field over current environmentally acceptable methods for oil recovery or separation from an aqueous/hydrocarbon oil admixture. There are currently few environmentally acceptable methods designed to remedy contamination of the subsurface due to leakage of hydrocarbon oils and hydrocarbon fuels from underground storage tanks. One such method requires flushing large amounts of fresh water down to the water table in an effort to entrain liquid contaminants that have not yet reached the water table, while drawing up contaminated water from the water table, concomitantly distilling off or otherwise separating out pure water from the contaminant, and then returning the purified water to the water table. The drawing up, purification and return cycle must be repeated at length, typically over the course of many years, until the concentration of contaminants in the water at the water table has fallen to environmentally acceptable levels.
The removal of hydrocarbon oils and other oil contaminants is further complicated when recovery and reuse of the contaminant, as well as its containment, is sought. Many containment processes and devices render recovery and reuse of the contaminant impossible; either because the contaminant is in a state of total or partial degradation, or the contaminant cannot be easily extracted from the absorbent means used in the chosen process.
Early suggestions for absorbing oils from liquid and solid surfaces involved the use of natural cellulose-containing materials such as sawdust, corn cobs, tree bark, and wood pulp to soak up the oil or other contaminant. The use of a natural product materials held in a netting or liner to absorb, and then remove, a contaminant has been disclosed. For example, U.S. Pat. No. 4,497,712 suggests an absorbent "pillow" designed to absorb chemical solutions and hydrocarbons from either solid or liquid surfaces. The "pillow" is filled with ground corn cobs which are made of an organic cellulose material. The use of dried bark from certain species of trees, held together in a tubular netting is suggested in U.S. Pat. No. 3,617,565. The "bark-in-netting" device is designed to absorb a variety of insoluble petroleum products from either a water or solid surface. U.S. Pat. No. 4,439,324 suggests bird feathers in mesh bags to effect removal of oil from the surface in open water. The use of many of these natural products is not practical or even feasible for widespread industrial use.
Fibrous cellulosic material, and especially fibrous cellulosic residues from paper-making or pulp-making has also been suggested to absorb oils and other hydrocarbons. U.S. Pat. No. 4,670,156 suggests this fibrous absorbent material can be used both in onshore and open water applications. Common cellulose sponge, such as household sponge may be esterified with one or more fatty acid esters and thereby rendered lipophilic so that it will absorb up to 10 times its weight of oily material, according to U.S. Pat. No. 3,915,855. Another patent, U.S. Pat. No. 3,677,982 suggests the use of a cellulose sponge pretreated with an unsaturated compound such as styrene or an acrylic compound and an organic peroxide to absorb floating petroleum oil from a water surface.
U.S. Pat. Nos. 3,632,361 and 4,412,947 disclose hydrophilic absorbent collagen mats and sponges, some of which are said to absorb 50 times their weight of water. A process for making collagen sponges is also disclosed in U.S. Pat. No. 3,823,212. Gelatin has been disclosed as a component for hydrophilic surgical sponge in U.S. Pat. No. 2,465,437.
Various synthetic products in various forms, such as polystyrene, polypropylene, etc. have been known and used as an absorbent for oil collection. However, the nonbiodegradability of these substances, as well as the difficulty of contaminant recovery from these synthetics, which inhibits the subsequent reuse of the collected contaminants, poses a significant obstacle which this invention seeks to overcome.
As evidenced by the aforementioned patents, and others, the use of collagen and gelatin sponges has been widely recognized in the medical field for many years.
The present invention uses the sponges made from various essentially fat-free foamable natural products such as animal proteins and plant polysaccharides, preferably collagen and gelatin, to absorb oils, especially hydrocarbon oils and other hydrocarbon fuels from an aqueous medium or aqueous-wetted surface to the extent of at least about 30 times their own weight, preferably at least about 50 times their weight. Other animal proteins and plant polysaccharides which are contemplated to be used include egg white albumen, vegetable gums such as gum agar, gum arabic, gum karaya, locust bean gum, and the like.
This discovery is most unexpected in view of the earlier disclosures which emphasized the hydrophilic properties of such sponges. It was not thought that such sponges would display an equal or greater absorbency preference for oils, especially hydrocarbon oils and other hydrocarbon fuels, over that for water.